1) Field of the Invention
The present invention relates to an image forming apparatus that uses electrophotography, like a copier apparatus, a facsimile apparatus or a printer.
2) Description of the Related Art
Conventionally, in an image forming apparatus, the slant of the bristle on a cleaning brush is a standard problem. To eliminate the unevenness of the coating of toner on a photosensitive drum arising due to the slant of the bristle on the cleaning brush, in some of the conventional image forming apparatuses an arrangement is provided that makes it possible to adjust the pressure of a lubricant in order. The cleaning brush and a cleaning blade that is included in a cleaning unit of the photosensitive drum removes the excess toner from the photosensitive drum. However, due to the presence of a slant of the bristle on the cleaning brush (the direction of the slant of the bristle on the cleaning brush is assumed to be towards the back), the toner is transferred on to the photosensitive drum in the direction opposite to the direction of the slant of the bristle on the cleaning brush. Due to this, the toner quantity picked by the cleaning blade varies, causing a difference in the frictional resistance between the cleaning blade and the photosensitive drum in the front and in the back.
Particularly, in the case in which the lubricant is externally added to the toner, the refilled toner gets consumed from the direction of the transference of the toner by a transfer screw in a developing unit. Due to this, the quantity of the lubricant that gets transferred to the photosensitive drum varies, the quantity of the lubricant being large in the front and diminishing towards the back. Hence, the lubricant is found in abundance in the toner on the side where a toner container is situated, that is, the front, and no lubricant is found in the toner on the opposite side, that is, the back. This causes a difference in the scraping of the photosensitive layer of the photosensitive drum in the front and the back. That is, the photosensitive layer on the back is lost early because of less lubricant, leading to imperfect cleaning.
It is an object of the present invention to provide an image forming apparatus that solves at least the problems mentioned above.
The image forming apparatus according to one aspect of the present invention comprises a photosensitive drum; a developing unit that causes a toner to adhere to the photosensitive drum, the developing unit including transferring screws that transfer a developer in the developing unit in a certain direction, and a developing roller situated near the transferring screws; and a cleaning unit that cleans excess toner on the photosensitive drum, the cleaning unit including a cleaning brush, wherein the cleaning brush has bristles that slant in the direction opposite to the direction of the developer transference by the transferring screws.
The image forming apparatus according to another aspect of the present invention comprises a photosensitive drum; a developing unit that causes a toner to adhere to the photosensitive drum; and a cleaning unit that cleans excess toner on the photosensitive drum, the cleaning unit including an excess toner removing coil that transfers excess toner in a certain direction, and a cleaning brush, wherein the cleaning brush has bristles that slant in the direction that is opposite to the direction of excess toner transference in the excess toner removing coil.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.